Substituted Carboxamide Corrosion Inhibitor Compounds

ABSTRACT

A method of inhibiting corrosion of a metal surface may include contacting the metal surface with a corrosion inhibitor compound that includes a substituted carboxamide.

BACKGROUND

Corrosion is one of the most problematic challenges in the production ofoil and gas. A common contributor to corrosion is acidic fluids. Acidicfluids are present in a multitude of operations in the oil and gasindustry. In operations using acidic well fluids, metal surfaces ofequipment such as piping, tubing, pumps, blending equipment, andumbilical lines may be exposed to the acidic fluid. The acidic fluidsmay include one or more of a variety of acids, such as hydrochloricacid, acetic acid, formic acid, hydrofluoric acid, or any combination ofsuch acids. In addition, many fluids used in the oil and gas industrymay include a water source that may incidentally contain certain amountsof acid, which, in turn, may cause the fluid to be at least slightlyacidic. Even weakly acidic fluids may be problematic in that they maycause corrosion of metals. Corrosion may occur anywhere in a wellproduction system or pipeline system.

Examples of common types of corrosion include, but are not limited to,the rusting of metal, the dissolution of metal in an acidic solution,and patina development on the surface of a metal. The expense ofreplacing corrosion damaged equipment is high. While the rate at whichcorrosion will occur depends on a number of factors such as metallurgy,chemical nature of the corrodent, salinity, pH, temperature, etc., somesort of corrosion almost inevitably occurs. One way to mitigate thisproblem includes using corrosion inhibitors in the hydrocarbonproduction system.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of theinvention, reference will now be made to the accompanying drawings inwhich:

FIG. 1 illustrates a well production system, according to someembodiments.

FIG. 2 demonstrates a comparison of inhibited corrosion rates fromautoclave tests at 250° F. (121° C.), according to some embodiments.

FIG. 3 depicts Kettle test results for synthesized carboxamides,according to some embodiments.

FIG. 4 depicts Kettle test results for synthesized carboxamides withacetic acid, according to some embodiments.

DETAILED DESCRIPTION

The present disclosure relates to inhibiting the corrosion of metalsurfaces and, more particularly, to the use of substituted carboxamidesas a corrosion inhibitor that is effective in oil and gas production.The methods, compositions and systems disclosed herein comprise singlecompounds that may effectively function as corrosion inhibitors. Thecorrosion inhibitor compounds may coat metal surfaces in acidicenvironments, thereby protecting said surfaces from corroding. This maybe advantageous as the minimum effective concentration of thesubstituted carboxamide present in the corrosion inhibitor compounds maybe lower than those currently used in industry. Additionally, thesubstituted carboxamide may be stable at higher temperatures than thosecurrently used.

For inhibition of corrosion, a corrosion inhibitor compound comprising asubstituted carboxamide may come into contact with metal surfacessusceptible to corrosion, alone or in combination with other fluids,such as treatment fluids or produced fluids. For example, the corrosioninhibitor compound comprising a substituted carboxamide may be preparedand then introduced into a wellbore such that corrosion of metalsurfaces (e.g., at surface, the wellhead, or downhole) that come intocontact with the fluid may be reduced. Alternatively, the corrosioninhibitor compound comprising a substituted carboxamide may be added toproduced fluids, either downhole or at the surface, such that corrosionof metal surfaces that come into contact with the produced fluids may bereduced. The metals that may be protected include, but are not limitedto, steel grade N-80, J-55, P-110, QT800, HS80, and other commonoilfield alloys, such as 13Cr, 25Cr, Incoloy 825, and 316L. Thecorrosion inhibitor compounds disclosed herein may comprise an aqueouscomponent. The corrosion inhibitor compounds may also be used alone, orwith other fluids, including, for example, with fluids that may furthercomprise an acid.

The corrosion inhibitor compounds may coat a metal surface in anysuitable manner. In some embodiments, the metal surfaces that may bedisposed downhole may be coated with the corrosion inhibitor before themetal surface is disposed downhole. The coating of the metal surface maybe achieved because the substituted carboxamide is a surfactant andbehaves accordingly. For example, the substituted carboxamide may form amonolayer at interfaces that may facilitate a lower energy state.Hydrophilic or more polar functional groups, such as amides and thiones,may be attracted to and may be adsorbed onto the surface of the metal.The adsorption of organic inhibitors on the metal surface may be includepi-bond orbital adsorption, electrostatic adsorption, chemisorption, orcombinations thereof.

Suitable substituted carboxamides may be prepared by any of a variety ofsuitable techniques. In some embodiments, a substituted carboxamide maybe synthesized by reacting equimolar amounts of a substituted orunsubstituted thiourea and a polyalkylene polyamine which may form aprimary amine or a secondary amine. The formed primary amine orsecondary amine may be any substituted amine in which at least onesubstituent is terminated by a five membered heterocyclic ring having atleast one thione group. In some embodiments, the substituted carboxamidemay be synthesized by reacting equimolar amount of substituted orunsubstituted urea and a polyalkylene polyamine. One of ordinary skillin the art, along with the present disclosure, may be able to select theappropriate reactants for a given application.

A substituted carboxamide may be formed by reacting the substitutedamine with a fatty acid. The substituted amine may be a primary amine ora secondary amine wherein at least one substituent may be terminated bya five-membered heterocyclic ring and wherein at least one pendant groupmay comprise a ketone group or a thione group. In some embodiments, theheterocyclic atoms in the five-membered ring may include at least onenitrogen atom. Any suitable fatty acid may be used, including, but notlimited to, carbonic acid, formic acid, acetic acid, propionic acid,butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid,pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylicacid, myristic acid, pentadecylic acid, palmitic acid, margaric acid,stearic acid, nonadecylic acid, arachidic acid, tall oil fatty acid, thelike, and/or any combination thereof. The amidization reaction may occurat a temperature of about 150° C. to about 200° C. and under atmosphericpressure.

The produced substituted carboxamide may be any suitable substitutedcarboxamide capable of providing corrosion inhibition properties fluids.In some embodiments, a substituted carboxamide wherein at least onesubstituent is terminated with a heterocyclic five-membered ring with atleast one pendent group comprising a ketone group or a thione group maybe used. Suitable substituted carboxamides may include, but are notlimited to, a substituted carboxamide of Formula (1) as follows:

wherein R₁ may be selected from the group consisting of a hydrogen, analky group, an alkenyl group, a heteroatom substituted alkyl group, or aheteroatom atom substituted alkenyl group, wherein R₂ may be a hydrogen,an alkyl group, an alkenyl group, a heteroatom substituted alkyl group,a heteroatom atom substituted alkenyl group, or an alkyl or alkenylgroup terminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof, wherein R₃ may be an alkyl or alkenyl groupterminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof. Suitable heteroatoms that may be substituted in R₁and/or R₂ may include, but are not limited to, nitrogen, oxygen, andsulfur, among others. The alkyl, alkenyl, or heteroatom substitutedgroups of R₁, R₂, and R₃ may be the same or different and, in someembodiments, may include 1 carbon atom to 20 carbon atoms.Alternatively, the alkyl, alkenyl, or heteroatom substituted groups ofR₁, R₂, and R₃ may include from 1 to 20 carbon atoms, from 4-15 carbonatoms, or from 5-10 carbon atoms. In some embodiments, the alkyl,alkenyl, or heteroatom substituted groups of R₁, R₂, and R₃ may includefrom 1 to 6 carbon atoms. For example, R₃ may be a chain of 2 to 4carbon atoms terminated by the five-member heterocyclic rings while R₁may be a chain of 6 to 20 carbon atoms.

Examples of suitable substituted carboxamides may depend on thereactants used to create said substituted carboxamide. An example of asuitable substituted carboxamide for use as a corrosion inhibitorcompounds, shown in Structure (2) below may be formed from reaction ofequimolar amounts of thiourea or urea and diethylenetriamine followed byreaction with a carboxylic acid, such as tall oil fatty acid.

wherein X₁ may be selected from the group consisting of a thione or aketone, wherein R₁ may be selected from the group consisting of ahydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group.

Another example of a suitable substituted carboxamide for use as acorrosion inhibitor compound may be formed from reaction of thiourea orurea and tetraethylenepentamine in a 2:1 molar ratio followed byreaction with a carboxylic acid, such as tall oil fatty acid, as shownbelow in Structure (3):

wherein X₁ may be individually selected from the group consisting of athione or a ketone, wherein R₁ is selected from the group consisting ofa hydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group.

In some embodiments, Structure (2) may be further reacted with asaturated diacid, an unsaturated diacid, a saturated anhydride, or anunsaturated anhydride to form a substituted carboxamide for use as thecorrosion inhibitor compound of Structure (4) as follows:

wherein X₁ may be individually selected from the group consisting of athione or a ketone, wherein R₁ is selected from the group consisting ofan alky group, an alkenyl group, a heteroatom substituted alkyl group,or a heteroatom atom substituted alkenyl group. In some embodiments,Structure (4) may function as a corrosion inhibitor, wherein thedistance between the two five-membered rings may be controlled byvarying R₁. In some embodiments as R₁ gets longer or shorter someproperties may be affected, such as solubility, viscosity, and meltingpoint. In another embodiment, Structure (2) or Structure (3) may befurther reacted with acids that include, but are not limited to, acrylicacid, acetic acid, thioglycolic acid, glycolic acid, methane sulfonicacid, phosphonic acid, or combinations thereof, to form corrosioninhibitor compounds comprising at least one acrylated five-memberedheterocyclic ring wherein at least one pendent group may comprise aketone group or a thione group, of Structure (5) and Structure (6),respectively, as follows:

wherein X₁ and X₂ may be individually selected from the group consistingof a thione or a ketone, wherein R₁ is selected from the groupconsisting of a hydrogen, an alky group, an alkenyl group, a heteroatomsubstituted alkyl group, or a heteroatom atom substituted alkenyl group,wherein Y is the radical derived from the acid listed above. It may beadvantageous to use the above acrylated formulas disclosed herein asthey may affect the solubility of the product. For example, dependingupon the application, greater or less water or brine solubility may bedesired.

In some embodiments, the corrosion inhibitor compounds disclosed hereinmay be provided in a solvent. Suitable solvents include, for example,methyl alcohol, ethyl alcohol, isopropyl alcohol, methanol, glycol,ethylene glycol, propylene glycol, dimethyl formamide, N-methylpyrrolidone, propylene glycol methyl ether, toluene, xylene, monobutylether, hexane, cyclohexane, 2-Butoxyethanol, any organic solvent,aromatic solvents and any combination thereof. In some embodiments, thesolvent may be present in an amount in a range of from about 50 wt. % toabout 99.5 wt. %, or about 65 wt. % to about 98 wt. %, or about 80 wt. %to about 90 wt. % based on a total weight of the solvent and thecorrosion inhibitor.

Methods are provided herein for adding one or more corrosion inhibitorcompounds to a fluid, wherein the fluid may comprise any one or more ofwater, a gas, a liquid hydrocarbon, and any combination thereof. Incertain embodiments, the method may comprise adding to the fluid aneffective amount of an embodiment of the corrosion inhibitor compoundsto inhibit, retard, reduce, control, delay, and/or the like theformation of corrosion on metal parts and materials.

It should be noted that the corrosion inhibitor compounds, and methodsof use thereof, as disclosed herein, may be introduced into a fluidcomprising one or more of water, a gas, a liquid hydrocarbon, or anycombination thereof. Although listed separately from liquid hydrocarbon,the gas may in some embodiments include gaseous hydrocarbon, though thegas need not necessarily include hydrocarbon. In certain embodiments,the corrosion inhibitor compound may be introduced into the fluidthrough a conduit or an injection point. In certain embodiments, one ormore corrosion inhibitor compounds may be introduced into a wellhead, awellbore, a subterranean formation, a conduit, a vessel, and the likeand may contact and/or be introduced into a fluid residing therein. Inat least one embodiment, the wellhead, wellbore, subterranean formation,conduit, vessel, or the like may be in a deepwater environment. In atleast one embodiment, the corrosion inhibitor compounds may beintroduced into the deepwater environment by way of an umbilical. Incertain embodiments, the fluid may be flowing, or it may besubstantially stationary. In some instances, the fluid may contact metalsurfaces. By introduction of the corrosion inhibitor compound into thefluid, corrosion of the metal surface may be inhibited.

In certain embodiments, the fluid may be within a vessel, or within aconduit (e.g., a conduit that may transport the fluid), or within asubterranean formation, or within a wellbore penetrating a portion ofthe subterranean formation, and/or within a wellhead of a wellbore.Examples of conduits include, but are not limited to, pipelines,production piping, subsea tubulars, process equipment, and the like asused in industrial settings and/or as used in the production of oiland/or gas from a subterranean formation, and the like. The conduit mayin certain embodiments penetrate at least a portion of a subterraneanformation, as in the case of an oil and/or gas well. In someembodiments, the wellhead may be in a deepwater environment. Inparticular embodiments, the conduit may be a wellhead, a wellbore, ormay be located within a wellbore penetrating at least a portion of asubterranean formation. The oil and/or gas well may be a subsea well(e.g., with the subterranean formation being located below the seafloor), or it may be a surface well (e.g., with the subterraneanformation being located belowground). In some embodiments, the subseawell may be in a deepwater environment.

In some embodiments, the corrosion inhibitor compounds of the presentdisclosure initially may be incorporated into a composition prior tobeing introduced into the fluid. The composition may be any suitablecomposition in which the corrosion inhibitor compound may be included.For example, the composition may include a solvent for the corrosioninhibitor compound. Suitable solvents include, for example, methylalcohol, ethyl alcohol, isopropyl alcohol, methanol, glycol, ethyleneglycol, propylene glycol, dimethyl formamide, N-methyl pyrrolidone,propylene glycol methyl ether, toluene, xylene, monobutyl ether, hexane,cyclohexane, 2-Butoxyethanol, any organic solvent, aromatic solvents andany combination thereof.

In some embodiments, the corrosion inhibitor compounds may be introducedinto a fluid in any suitable amount for corrosion inhibition. In variousembodiments, the corrosion inhibitor compounds of the present disclosuremay be used as low dosage corrosion inhibitors such that an effectiveconcentration of actives in one or more corrosion inhibitor compoundsfor inhibiting, retarding, mitigating, reducing, controlling, and/ordelaying corrosion may from about 2 ppm to about 1,000 ppm by volume.Alternatively, the concentrations of actives may be from about 2 ppm toabout 1,000 ppm, about 2.25 ppm to about 900 ppm, about 2.5 ppm to about800 ppm, about 2.75 ppm to about 700 ppm, about 3 ppm to about 600 ppm,about 3.25 ppm to about 500 ppm, about 3.5 ppm to about 400 ppm, about3.75 ppm to about 300 ppm, about 4 ppm to about 200 ppm, about 4.5 ppmto about 100 ppm, or about 5 ppm to about 50 ppm by volume. In someembodiments, the corrosion inhibitor compounds may be suitable inapplications with temperatures up to 350° F. (177° C.) under pressuresof about 1 atm to about 300 atms.

In certain embodiments, the corrosion inhibitor compounds may beintroduced into a wellhead of a wellbore penetrating at least a portionof the subterranean formation, a wellbore, a subterranean formation, avessel, and/or a conduit (and/or into a fluid within any of theforegoing) using any method or equipment known in the art. In otherembodiments, a corrosion inhibitor compound of the present disclosuremay be injected into a portion of a subterranean formation using anannular space or capillary injection system to continuously introducethe corrosion inhibitor compound into the formation. In someembodiments, the capillary injection may include an umbilical with thewellhead in a deepwater environment. In certain embodiments, acomposition comprising a corrosion inhibitor compound of the presentdisclosure may be circulated in the wellbore using the same types ofpumping systems and equipment at the surface that may be used tointroduce fluids or additives into a wellbore penetrating at least aportion of the subterranean formation.

Accordingly, this disclosure describes methods, systems, andcompositions that may use a substituted carboxamide as corrosioninhibitor compounds. The methods, systems, and compositions may includeany of the following statements:

Statement 1. A method of inhibiting corrosion of a metal surface maycomprise contacting the metal surface with a corrosion inhibitorcompound comprising a substituted carboxamide.

Statement 2. The method of statement 1, further comprising coating themetal surface with the corrosion inhibitor compound.

Statement 3. The method of statement 1 or 2, further comprisingintroducing the corrosion inhibitor compound into a wellbore, whereinthe metal surface is disposed in the wellbore.

Statement 4. The method of any of the preceding statements, wherein thesubstituted carboxamide comprises the molecular formula: R₁C(O)NR₂R₃,wherein R₁ is selected from the group consisting of a hydrogen, an alkylgroup, an alkenyl group, a heteroatom substituted alkyl group, or aheteroatom atom substituted alkenyl group; wherein R₂ is a hydrogen, analky group, an alkenyl group, a heteroatom substituted alkyl group, aheteroatom atom substituted alkenyl group, or an alkyl or alkenyl groupterminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof; and wherein R₃ is an alkyl or alkenyl groupterminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof.

Statement 5. The method of any of the preceding statements, wherein thesubstituted carboxamide comprises the molecular formula:

wherein X₁ is selected from the group consisting of a thione or aketone, and wherein R₁ is selected from the group consisting of ahydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group.

Statement 6. The method of any of the preceding statements, wherein thesubstituted carboxamide comprises the molecular formula:

wherein X₁ is individually selected from the group consisting of athione or a ketone; and wherein R₁ is selected from the group consistingof a hydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group.

Statement 7. The method of any of the preceding statements, wherein thesubstituted carboxamide comprises the molecular formula:

wherein X₁ is individually selected from the group consisting of athione or a ketone, and wherein R₁ is selected from the group consistingof an alky group, an alkenyl group, a heteroatom substituted alkylgroup, or a heteroatom atom substituted alkenyl group.

Statement 8. The method of any of the preceding statements, wherein thesubstituted carboxamide is present in the fluid in an amount of fromabout 10 ppm to about 500 ppm.

Statement 9. The method of any of the preceding statements, wherein thecorrosion inhibitor compound is provided in a solvent selected from thegroup consisting of methyl alcohol, ethyl alcohol, isopropyl alcohol,methanol, glycol, ethylene glycol, propylene glycol, dimethyl formamide,N-methyl pyrrolidone, propylene glycol methyl ether, toluene, xylene,monobutyl ether, hexane, cyclohexane, 2-Butoxyethanol, any organicsolvent, aromatic solvents and any combination thereof.

Statement 10. The method of statement 3, wherein the introducing thecorrosion inhibitor compound into the wellbore comprises pumping thecorrosion inhibitor compound from a fluid supply, through a productiontubing, and into the wellbore, and mixing the corrosion inhibitorcompound with a produced fluid.

Statement 11. The method of statement 10, further comprisingtransporting the corrosion inhibitor compound mixed with the producedfluid to a surface of the wellbore, and coating at least one metalsurface in which the corrosion inhibitor compound mixed with theproduced fluid contacts.

Statement 12. The method of statement 4, wherein R₂ is a heteroatomsubstituted five-membered heterocyclic ring with at least one pendentgroup comprising a ketone group or a thione group.

Statement 13. The method of statement 12, wherein the heteroatomsubstituted five-membered heterocyclic ring comprises nitrogen.

Statement 14. The method of statement 5, wherein the substitutedcarboxamide is alkylated.

Statement 15. The method of statement 6, wherein the substitutedcarboxamide is alkylated.

Statement 16. The method of statement 9 wherein the solvent is presentin an amount of about 50 wt % to about 99.5 wt % based on the totalweight of the solvent and the corrosion inhibitor.

Statement 17. A corrosion inhibitor may comprise: a solvent package; anda corrosion inhibitor compound comprising a substituted carboxamidehaving the formula: R₁C(O)NR₂R₃, wherein R₁ is selected from the groupconsisting of a hydrogen, an alky group, an alkenyl group, a heteroatomsubstituted alkyl group, or a heteroatom atom substituted alkenyl group,wherein R₂ is a hydrogen, an alky group, an alkenyl group, a heteroatomsubstituted alkyl group, a heteroatom atom substituted alkenyl group, oran alkyl or alkenyl group terminated by a five-membered heterocyclicring with at least one pendent group comprising a ketone group, a thionegroup, or any combination thereof, and wherein R₃ is an alkyl or alkenylgroup terminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof.

Statement 18. The method of statement 17 wherein the solvent packagecomprises solvent selected from the group consisting of methyl alcohol,ethyl alcohol, isopropyl alcohol, ethylene glycol, propylene glycol,dimethyl formamide, N-methyl pyrrolidone, propylene glycol methyl ether,butyl cellulose, aromatic solvents, and combinations thereof.

Statement 19. A system for introducing a corrosion inhibitor into awellbore may comprise: a fluid supply containing the corrosioninhibitor, wherein the corrosion inhibitor comprises a corrosioninhibitor compound and a solvent package, wherein the corrosioninhibitor compound comprises a substituted carboxamide; and a tubular ina wellbore in a subterranean formation, wherein the tubular is in fluidcommunication with the corrosion inhibitor supply.

Statement 20. A system according to statement 19, wherein thesubstituted carboxamide has the formula: R₁C(O)NR₂R₃, wherein R₁ isselected from the group consisting of a hydrogen, an alky group, analkenyl group, a heteroatom substituted alkyl group, or a heteroatomatom substituted alkenyl group, wherein R₂ is a hydrogen, an alky group,an alkenyl group, a heteroatom substituted alkyl group, a heteroatomatom substituted alkenyl group, or an alkyl or alkenyl group terminatedby a five-membered heterocyclic ring with at least one pendent groupcomprising a ketone group, a thione group, or any combination thereof,and wherein R₃ is an alkyl or alkenyl group terminated by afive-membered heterocyclic ring with at least one pendent groupcomprising a ketone group, a thione group, or any combination thereof.

FIG. 1 illustrates a well production system. An example system 100 forintroduction of corrosion inhibitor compounds described herein into awellbore 118 is shown. Well system 100 may comprise a wellbore 118formed within a formation 104. Wellbore 118 may be a vertical wellboreas illustrated or it may be a horizontal and/or a directional well.While well system 100 may be illustrate as land-based, it should beunderstood that the present techniques may also be applicable inoffshore applications. Formation 104 may be comprised of severalgeological layers and may include one or more hydrocarbon reservoirs. Asillustrated, well system 100 may include a production tree 106 and awellhead 112 located at a well site 110. A production tubing 124 mayextend from wellhead 112 into wellbore 118, which may traverse formation114.

The wellbore 118 may be cased with one or more casings 114. Casing 114may support and maintain the structure of wellbore 118 and preventwellbore 118 from collapsing. In some embodiments, a portion of the wellmay not be cased and may be referred to as “open hole.” The spacebetween production tubing 124 and casing 126 or wellbore wall 118 may bean annulus 134. Production fluid 138 may enter annulus 134 fromformation 114 and then may enter production tubing 124 from annulus 134.Production tubing 124 may carry production fluid 138 uphole toproduction tree 106. Production fluid 138 may then be delivered tovarious surface facilities for processing via a surface pipeline 120.

As illustrated, corrosion inhibitor compounds 150 may be introduced intoannulus 134 between production tubing 124 and casing 136. As previouslydescribed, corrosion inhibitor compounds 150 may be used alone, or theymay be added to produced fluids, treatment fluids, and other additives.Corrosion inhibitor compounds 150 may be introduced into wellbore 118 inany suitable manner. In some embodiments, corrosion inhibitor compounds150 may be injected into wellbore 118 at wellhead 112. In an embodiment,corrosion inhibitor compounds 150 may be continuously provided towellbore 118. Suitable techniques for introduction of corrosioninhibitor compounds 150 may include, but are not limited to, neatannulus drip, slip stream, capillary string, or batch processes. Asillustrated, corrosion inhibitor compounds 150 may be introduced towellbore at wellhead 112 by way of neat annulus drip. Corrosioninhibitor compounds may flow through wellhead 112 and into annulus 134formed between production tubing 124 and casing 136. Corrosion inhibitorcompounds 150 may fall and/or drip to the bottom of wellbore 118. At thebottom of wellbore 132, corrosion inhibitor compounds 150 may mix withthe produced fluids 138. The mixture 142 of corrosion inhibitorcompounds 150 and produced fluids 138 may then be pumped throughdownhole tools 140 and up production tubing 124. As the mixture 142 ofcorrosion inhibitor compounds 150 and the produced fluids 138 flowthrough production tree 106, the corrosion inhibitor compounds 150 andthe produced fluids 138 may continuously be in contact with productiontubing 124, slickline 122, and downhole tools 140, in turn which mayprovide production tubing 124, slickline 122, and downhole tools 140with corrosion resistance. This provided corrosion resistance may reducethe corrosion on said metal components of well system 100 and in turnextend the production life of said metal components.

In some embodiments, with continued reference to the FIG. 1 , wellsystem 100 may be used for delivery of corrosion inhibitor compounds 150into wellbore 118. Corrosion inhibitor compounds 150 may be pumped fromfluid supply (not shown) down the interior of production tubing 124 inwellbore 118. Corrosion inhibitor compounds 150 may be allowed to flowdown the interior of production tubing 124. Corrosion inhibitorcompounds 150 may exit production tubing 124 and mix with producedfluids 138. Fluid 130 comprising a corrosion inhibitor may coat anymetal surface in which corrosion inhibitor compounds 150 may contactwhile being placed downhole. Additionally, corrosion inhibitor compounds150 that may be mixed with produced fluid 138 may be brought back to thesurface and may coat any metal surface in which the mixture fluid 142may come in contact with.

The disclosed corrosion inhibitor compounds may also directly orindirectly affect the various downhole equipment and tools that may comeinto contact with the corrosion inhibitor compounds during operation.Such equipment and tools may include, but are not limited to, wellborecasing, wellbore liner, completion string, insert strings, drill string,coiled tubing, slickline, wireline, drill pipe, drill collars, mudmotors, downhole motors and/or pumps, surface-mounted motors and/orpumps, centralizers, turbolizers, scratchers, floats (e.g., shoes,collars, valves, etc.), logging tools and related telemetry equipment,actuators (e.g., electromechanical devices, hydromechanical devices,etc.), sliding sleeves, production sleeves, plugs, screens, filters,flow control devices (e.g., inflow control devices, autonomous inflowcontrol devices, outflow control devices, etc.), couplings (e.g.,electro-hydraulic wet connect, dry connect, inductive coupler, etc.),control lines (e.g., electrical, fiber optic, hydraulic, etc.),surveillance lines, drill bits and reamers, sensors or distributedsensors, downhole heat exchangers, valves and corresponding actuationdevices, tool seals, packers, cement plugs, bridge plugs, and otherwellbore isolation devices, or components, and the like. Any of thesecomponents may be included in the systems generally described above anddepicted in FIG. 1 .

Example 1

FIG. 2 demonstrates a comparison of inhibited corrosion rates fromautoclave tests at 250° F. (121° C.). The synthesized carboxamides testsall contained 10 ppm of actives based on the brine volume. The resultsshown in FIG. 2 illustrate the effectiveness of the synthesizedcarboxamide corrosion inhibitor compounds as evaluated in a series ofautoclave tests. Each test contained 1.17 liters of synthetic fieldbrine, 430 ml of kerosene and a single UNS10180 coupon (27.88 cm²). Thetest solutions were deaerated and saturated with CO₂ at a partialpressure of 19.6 psia (135 KPa), stirred with an inline mixer (1,500rpm) and heated to 250° F. (121° C.). The corrosion inhibitor compoundswere formulated by adding 1 gram of actives to 10 grams of solvent (9%active). The corrosion inhibitor compounds were then injected into thetest solutions at 112 ppm, which equates to 10 ppm of actives. The timefor completion of the tests ranged from 20 hours to 23 hours. Uponcompletion of the tests, the coupons were removed from the autoclavesand cleaned in an inhibited acid bath according to ASTM G1 C.3.5. Asshown in FIG. 2 , the synthesized products outperformed two commonlyused corrosion inhibitor intermediates and several formulated productsthat are currently used in the oilfield. Intermediates A and A+Cresulted in a corrosion rates of 87.7 mpy and 120 mpy, respectively.Formulations Z, Y, and X resulted in corrosion rates of 44 mpy, 151.7mpy, and 139.9 mpy, respectively. The TEPA/Thiourea/Myristic Acidcomposition resulted in a corrosion rate of 20.2 mpy. TheDETA/Thiorea/Myristic Acid composition resulted in a corrosion rate of22.5 mpy. The DETA/Thiourea/Lauric Acid composition resulted in acorrosion rate of 27.6 mpy. The compositions of intermediates A, C, X,Y, and Z in FIG. 2 are shown in Table 1.

TABLE 1 Corrosion Treatment Formulation Inhibitor Active Rate Solvent(%) (%) (ppm) Intermediate methanol (50)/ imidazoline (8) 150 A ethyleneglycol (42) Intermediate methanol (48)/ imidazoline (8)/ 145 C ethyleneglycol phosphate ester (39.5) (4.5) Formulation water (71)/ethylenecomplex mixture 200 X glycol (15) (4%) Formulation water (53)/ complexmixture 200 Y methanol (25)/ (7.7%) ethylene glycol (7) Formulationwater (56)/ imidazoline (8)/ 200 Z methanol (15) quaternary amine(1)/mercaptan (2)

Example 2

FIG. 3 depicts Kettle test results for unsalted synthesized carboxamidesusing Structures (2) and (3) as shown above in accordance with ASTMG31—Standard Practice for Laboratory Immersion Corrosion Testing ofMetals and ASTM G170—Standard Guide for Evaluating and QualifyingOilfield and Refinery Corrosion Inhibitors in the Laboratory. The Kettletests were continuously purged with anaerobic grade CO₂, having apartial pressure of 10.8 psia (74 KPa), 800 ml of sea-salt brine, 80 mlof kerosene, heated to 150° F. (66° C.) and stirred with a magnetic stirbar/plate. The synthesized carboxamides were dissolved in methanol (5%actives) and injected at 100 ppm (5 ppm actives) and then up to 200 ppm(10 ppm actives), based on the total test volume.

A Kettle test using a first composition comprising Structure (2)included a mixture of 38.05 g (0.5 mole) of thiourea and 51.6 g (0.5mole) of diethylenetriamine (DETA). The mixture was charged to a 250-mLglass kettle equipped with a condenser, a stirrer, and a gas inlet tube.A slow nitrogen sparge was started. Using an electric heating mantle,the mixture was slowly heated to 170° C. while stirring. The reactiontemperature was kept at 170° C. for 4 hours. The mixture was cooled downto 100° C. and lauric acid (100.16 g, 0.5 mole) was added. The mixturewas heated back to 170° C. and kept at this temperature for 4 hours withnitrogen purging.

A Kettle test using a second composition comprising Structure (2)included a mixture of 38.05 g (0.5 mole) of thiourea and 51.6 g (0.5mole) of diethylenetriamine (DETA) was charged to a 250-mL glass kettleequipped with a condenser, a stirrer and a gas inlet tube. A slownitrogen sparge was started. Using an electric heating mantle, themixture was slowly heated to 170° C. while stirring. The reactiontemperature was kept at 170° C. for 4 hours. The mixture was cooled downto 100° C. and myristic acid (114.2 g, 0.5 mole) was added. The mixturewas heated back to 170° C. and kept at this temperature for 4 hours withnitrogen purging.

A Kettle test using a composition comprising Structure (3) included amixture of 76.1 g (1.0 mole) of thiourea and 94.7 g (0.5 mole) oftetraethylenepentamine (TEPA) was charged to a 250-mL glass kettleequipped with a condenser, a stirrer and a gas inlet tube. A slownitrogen sparge was started. Using an electric heating mantle, themixture was slowly heated to 170° C. while stirring. The reactiontemperature was kept at 170° C. for 4 hours. The mixture was cooled downto 100° C. and myristic acid (114.2 g, 0.5 mole) was added. The mixturewas heated back to 170° C. and kept at this temperature for 4 hours withnitrogen purging.

The baseline or uninhibited corrosion rate was monitored for 0.85 hoursbefore the corrosion inhibitors were injected at 100 ppm (5 ppmactives). At a treatment rate of 100 ppm (5 ppm actives), the averagebaseline corrosion rate was reduced from 174 mils per year (“MPY”) to35, 77 and 4 MPY for the DETA/Thiourea/Lauric, DETA/Thiourea/Myristicand TEPA/Thiourea/Myristic reaction product, as depicted in FIG. 3 .This resulted in inhibition efficiencies of 80, 56 and 97%,respectively. The treatment rate was increased to 200 ppm (10 ppmactives total) at the 4 hour mark for the DETA/Thiourea/Lauric andDETA/Thiourea/Myristic tests, which reduced the corrosion rates to 7 MPY(96% inhibition efficiency) and 62 MPY (64% inhibition efficiency),respectively.

Example 3

FIG. 4 depicts Kettle test results for synthesized carboxamides saltedwith acetic acid in accordance with ASTM G31—Standard Practice forLaboratory Immersion Corrosion Testing of Metals and ASTM G170—StandardGuide for Evaluating and Qualifying Oilfield and Refinery CorrosionInhibitors in the Laboratory. As depicted in FIG. 4 , the synthesizedcarboxamides were evaluated with Kettle tests run with 810 ml ofsea-salt brine, 90 ml of kerosene, and continuously purged withanaerobic grade CO₂, with a partial pressure of 10.8 psia (74 KPa). TheKettle tests were heated to 150° F. (66° C.) and stirred with a magneticstir bar/plate. 1.5 grams of synthesized carboxamides were dissolved in28.5 grams of methanol and 1.5 grams of acetic acid (5% actives), theninjected at 100 ppm (5 ppm actives) up to 200 ppm (10 ppm actives),based on the total test volume. Instantaneous corrosion ratemeasurements were made with an electrochemical measurement system, usinga potentiostat and a linear polarization resistance technique inaccordance with ASTM G3—Standard Practice for Conventions Applicable toElectrochemical Measurements in Corrosion Testing. The potentiostat useda working electrode and a reference electrode and controlled the voltagedifference between the working electrode and the reference electrode.Both electrodes were contained in an electrochemical cell, where thepotentiostat was used to measure the current flow between the workingand reference electrodes. The free-corroding potential, or the potentialof the metal in the absence of any net current flow, was scanned overrange of +/−13 mV at a rate of 0.4 mV/second. It should be noted thatfree corrosion potential is the absence of a net electrical current thatflows to and from a metal's surface. The free corrosion potential ismeasured through the voltage difference between the immersed metal andthe appropriate reference electrode in a given environment.

It should be noted that the efficiency of a corrosion inhibitor may becalculated by the following formula: InhibitorEfficiency(%)=100×(CR_(uninhibited)−CR_(inhibited))/CR_(uninhibited),where CR_(uninhibited)=the corrosion rate of the uninhibited system, andCR_(inhibited)=the corrosion rate of the inhibited system. In general,the efficiency of a corrosion inhibitor increases with an increase ininhibitor concentration.

These tests were repeated with the addition of acetic acid (3.2% w/w) tothe diluted products. As shown in FIG. 4 , the Kettle tests wererepeated with the addition of acetic acid (3.2% w/w) to the dilutedproducts. The performance of the DETA/Thiourea/Lauric andDETA/Thiourea/Myristic inhibitors improved when salted with acetic acid.At a treatment rate of 100 ppm (5 ppm actives), the average baselinecorrosion rate was reduced from 182 MPY to 14, 42 and 17 MPY for theDETA/Thiourea/Lauric, DETA/Thiourea/Myristic and TEPA/Thiourea/Myristicreaction product. This equates to inhibition efficiencies of 92, 77 and91%, respectively. The treatment rate was increased to 200 ppm (10 ppmactives total) at the 3.5-hour mark for the DETA/Thiourea/Lauric andDETA/Thiourea/Myristic tests, which reduced the corrosion rates to 2 MPY(99% inhibition) and 26 MPY (86% inhibition), respectively. The finalinhibition efficiency for the TEPA/Thiourea/Myristic reaction productremained unchanged at 97%.

The foregoing has broadly outlined the features and technical advantagesof the embodiments disclosed herein so that the detailed description ofthe invention that follows may be better understood. Additional featuresand advantages of the invention may be described hereinafter that formthe subject of the claims of the invention. It should be appreciated bythose skilled in the art that the conception and the specificembodiments disclosed may be readily utilized as a basis for modifyingor designing other embodiments for carrying out the same purposes of thepresent invention. It should also be realized by those skilled in theart that such equivalent embodiments do not depart from the spirit andscope of the invention as set forth in the appended claims.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations may be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. A method of inhibiting corrosion of a metalsurface, comprising: contacting the metal surface with a corrosioninhibitor compound comprising a substituted carboxamide.
 2. The methodof claim 1, further comprising coating the metal surface with thecorrosion inhibitor compound.
 3. The method of claim 1 furthercomprising introducing the corrosion inhibitor compound into a wellbore,wherein the metal surface is disposed in the wellbore.
 4. The method ofclaim 1, wherein the substituted carboxamide comprises the molecularformula:R₁C(O)NR₂R₃ wherein R₁ is selected from the group consisting of ahydrogen, an alkyl group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group; wherein R₂is a hydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, a heteroatom atom substituted alkenyl group, or an alkyl oralkenyl group terminated by a five-membered heterocyclic ring with atleast one pendent group comprising a ketone group, a thione group, orany combination thereof; and wherein R₃ is an alkyl or alkenyl groupterminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof.
 5. The method of claim 1, wherein the substitutedcarboxamide comprises the molecular formula:

wherein X₁ is selected from the group consisting of a thione or aketone, and wherein R₁ is selected from the group consisting of ahydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group.
 6. Themethod of claim 1, wherein the substituted carboxamide comprises themolecular formula:

wherein X₁ is individually selected from the group consisting of athione or a ketone; and wherein R₁ is selected from the group consistingof a hydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group.
 7. Themethod of claim 1, wherein the substituted carboxamide comprises themolecular formula:

wherein X₁ is individually selected from the group consisting of athione or a ketone, and wherein R₁ is selected from the group consistingof an alky group, an alkenyl group, a heteroatom substituted alkylgroup, or a heteroatom atom substituted alkenyl group.
 8. The method ofclaim 1, wherein the substituted carboxamide is present in the fluid inan amount of from about 10 ppm to about 500 ppm.
 9. The method of claim1, wherein the corrosion inhibitor compound is provided in a solventselected from the group consisting of methyl alcohol, ethyl alcohol,isopropyl alcohol, methanol, glycol, ethylene glycol, propylene glycol,dimethyl formamide, N-methyl pyrrolidone, propylene glycol methyl ether,toluene, xylene, monobutyl ether, hexane, cyclohexane, 2-Butoxyethanol,any organic solvent, aromatic solvents and any combination thereof. 10.The method of claim 3, wherein the introducing the corrosion inhibitorcompound into the wellbore comprises pumping the corrosion inhibitorcompound from a fluid supply, through a production tubing, and into thewellbore, and mixing the corrosion inhibitor compound with a producedfluid.
 11. The method of claim 10, further comprising transporting thecorrosion inhibitor compound mixed with the produced fluid to a surfaceof the wellbore, and coating at least one metal surface in which thecorrosion inhibitor compound mixed with the produced fluid contacts. 12.The method of claim 4, wherein R₂ is a heteroatom substitutedfive-membered heterocyclic ring with at least one pendent groupcomprising a ketone group or a thione group.
 13. The method of claim 12,wherein the heteroatom substituted five-membered heterocyclic ringcomprises nitrogen.
 14. The method of claim 5, wherein the substitutedcarboxamide is alkylated.
 15. The method of claim 6, wherein thesubstituted carboxamide is alkylated.
 16. The method of claim 9 whereinthe solvent is present in an amount of about 50 wt % to about 99.5 wt %based on the total weight of the solvent and the corrosion inhibitor.17. A corrosion inhibitor comprising: a solvent package; and a corrosioninhibitor compound comprising a substituted carboxamide having theformula:R₁C(O)NR₂R₃ wherein R₁ is selected from the group consisting of ahydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group, wherein R₂is a hydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, a heteroatom atom substituted alkenyl group, or an alkyl oralkenyl group terminated by a five-membered heterocyclic ring with atleast one pendent group comprising a ketone group, a thione group, orany combination thereof, and wherein R₃ is an alkyl or alkenyl groupterminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof.
 18. The method of claim 17 wherein the solventpackage comprises solvent selected from the group consisting of methylalcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, propyleneglycol, dimethyl formamide, N-methyl pyrrolidone, propylene glycolmethyl ether, butyl cellulose, aromatic solvents, and combinationsthereof.
 19. A system for introducing a corrosion inhibitor into awellbore, comprising: a fluid supply containing the corrosion inhibitor,wherein the corrosion inhibitor comprises a corrosion inhibitor compoundand a solvent package, wherein the corrosion inhibitor compoundcomprises a substituted carboxamide; and a tubular in a wellbore in asubterranean formation, wherein the tubular is in fluid communicationwith the corrosion inhibitor supply.
 20. A system according to claim 19,wherein the substituted carboxamide has the formula:R₁C(O)NR₂R₃ wherein R₁ is selected from the group consisting of ahydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, or a heteroatom atom substituted alkenyl group, wherein R₂is a hydrogen, an alky group, an alkenyl group, a heteroatom substitutedalkyl group, a heteroatom atom substituted alkenyl group, or an alkyl oralkenyl group terminated by a five-membered heterocyclic ring with atleast one pendent group comprising a ketone group, a thione group, orany combination thereof, and wherein R₃ is an alkyl or alkenyl groupterminated by a five-membered heterocyclic ring with at least onependent group comprising a ketone group, a thione group, or anycombination thereof.